package listbyorder.access001_100.test2;

import listbyorder.utils.ListNode;

import java.util.List;

/**
 * @author code_yc
 * @version 1.0
 * @date 2020/6/17 10:34
 */
public class Solution1 {

    /*
    思路：
        同时遍历两个链表，链表为null，此位为0，直到两个链表同时为0的时候结束
        使用进位变量carry保存中间过程产生的进位
        遍历结束之后检查是否有进位
        如果有进位则将进位累加进链表最后
     */
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode pre = new ListNode(0);
        ListNode cur = pre;
        int carry = 0;
        while (l1 != null || l2 != null) {
            int x = l1 == null ? 0 : l1.val;
            int y = l2 == null ? 0 : l2.val;
            int sum = x + y + carry;
            carry = sum / 10;
            sum = sum % 10;
            cur.next = new ListNode(sum);
            cur = cur.next;
            if (l1 != null) l1 = l1.next;
            if (l2 != null) l2 = l2.next;
        }
        if (carry == 1) {
            cur.next = new ListNode(carry);
        }
        return pre.next;
    }

}
